Thin-walled plain bearings, as are presently used mainly by engine manufacturers, are mostly provided with mounting lugs. Such lugs are normally made by an impact tool, by means of which a small portion of the bearing surface is bent outwards at the joint face. In this way an external lug is formed; however in the sliding surface a corresponding depression is provided. These lugs serve mostly to aid installation so that the plain bearings cannot be incorrectly mounted.
The lugs can, in addition, prevent or at least hinder slow movement of the plain bearing during operation, both in the axial and in the peripheral directions. The receiving hole in the housing has a notch corresponding to the lug in which the lug engages.
Also other devices serve as assembly aids. So for instance it is known to make in an apex of the bearing a so-called wart by the impression of a stamping tool from the interior. The wart is an elevation on the outer part of the bearing and during manufacture a corresponding depression is simultaneously produced in the sliding surface of the bearing. Other fixing methods include e.g. the provision of a hole in the bearing and the insertion of a retention dowel or locating peg in the hole. This method is, however, expensive because the locating peg must be very accurately made (i.e. with narrow tolerances) to perfectly sit in the hole in the housing. In addition it must be provided with a shoulder so that if it becomes loose it will not move into the bearing which could result in breakdown. Blind holes may be made in thicker bearing liners so as to prevent the peg from travelling. Even in this case, however there must be a good fit between the peg and the corresponding hole in the casing.
The depression frequently formed on the inner surface (sliding surface) of the bearing necessarily causes disturbance in the buildup of the film of lubricant and consequently gives rise to a local reduction of loading capacity. Such lugs or other depressions are for these reasons situated as much as possible at a place where the loading of the bearing is small. This is not possible in many cases and this results, if allowed by the design, in possible widening of the bearing and therefore increased friction. If no fixing is provided there is an increased risk for reasons which have already been described.